In recent years, remarkable development of a functional card such as an IC tag and an IC card has been achieved, and the functional card has come into use in an anti-theft tag, a tag for checking those coming in and out, a telephone card, a credit card, a prepaid card, a cash card, an ID card, a card key, a variety of membership cards, a bookstore gift card, a patient registration card, a commuter pass, and the like. Each of these antenna circuit constituent bodies for the functional cards is constituted of: a base material formed of a resin film such as a polypropylene (PP) film and a polyethylene terephthalate (PET) film; and an antenna circuit pattern layer formed of metal foil of aluminum foil or copper foil, which is formed on a surface of the base material. The metal foil is bonded on one side or both sides of the base material with an adhesive interposed therebetween by employing a dry laminate method or the like, and thereafter, the metal foil is subjected to etching processing, thereby forming the antenna circuit pattern layer on the surface of the base material.
The conventional antenna circuit constituent body having the above-mentioned configuration and the conventional method for manufacturing the antenna circuit constituent body are disclosed in Japanese Patent Application Laid-Open Publication No. 2002-7990 (Patent Literature 1) and Japanese Patent Application Laid-Open Publication No. 2004-140587 (Patent Literature 2).
In the conventional antenna circuit constituent body for RFID, in general, pattern layers of a circuit are formed on both surfaces of a base material formed of a resin film. On one of the surfaces of the base material, a coiled pattern layer of an antenna circuit is formed. This pattern layer of the antenna circuit corresponds to a coil of an electronic circuit, also plays a role of an antenna receiving electromagnetic waves, and is referred to as the so-called coil pattern. On the other of the surfaces of the base material on a side opposite to the side on which the coiled circuit pattern layer is formed, a pattern layer of a circuit playing a role of a jumper of the above-mentioned antenna circuit is formed. This pattern layer of the circuit is referred to as the so-called bridge circuit pattern layer.
In the above-described antenna circuit constituent body, as a method of electrically connecting the antenna circuit pattern layer formed on the one of the surfaces of the base material and the bridge circuit pattern layer formed on the other of the surfaces of the base material, the below-described methods are available.
(1) On a side of a base material, opposite to a side thereof on which an antenna circuit pattern layer is formed, a bridge circuit pattern layer is formed. At respective portions of both end portions of the antenna circuit pattern layer and both end portions of the bridge circuit pattern layer, which are to be joined, through-holes are formed. The through-holes are filled with a plating material or a silver coating material, thereby connecting the both end portions of the antenna circuit pattern layer and the both end portions of the bridge circuit pattern layer.
(2) As disclosed in Japanese Patent Application Laid-Open Publication No. 2002-7990 (Patent Literature 1) and Japanese Patent Application Laid-Open Publication No. 2004-140587 (Patent Literature 2), on a side of a base material, opposite to a side thereof on which an antenna circuit pattern layer is formed, a bridge circuit pattern layer is formed. By means of a crimping process, respective portions of both end portions of the antenna circuit pattern layer formed on the one side of the base material and both end portions of the bridge circuit pattern layer formed on the opposite other side of the base material are connected. Here, the crimping process is conducted, for example, such that by means of ultrasonic waves or the like, at least portions of circuit pattern layers formed on both surfaces of the base material, with an adhesive interposed therebetween, are pressed against each other, thereby partially destroying resins constituting the adhesive, the base material, and the like and causing the portions of the circuit pattern layers on the both sides to physically contact each other.
(3) As disclosed in Japanese Patent Application Laid-Open Publication No. 2008-269161 (Patent Literature 3), on a side of a base material, opposite to a side thereof on which an antenna circuit pattern layer is formed, a bridge circuit pattern layer is formed. By means of resistance welding, the antenna circuit pattern layer formed on the one side of the base material and the bridge circuit pattern layer formed on the opposite other side of the base material are connected. In this case, in a state where welding electrodes are caused to contact a front side and a back side of a circuit pattern layer and a pressure is exerted thereon, heating is conducted by applying a predetermined current to the welding electrodes, thereby fusing one portion of the base material interposed between the front side of the circuit pattern layer and the back side of the circuit pattern layer and also causing portions of the front side of the circuit pattern layer and the back side of the circuit pattern layer, which face each other, to contact each other. To the portions of the circuit pattern layers on the front side and the back side, which have been caused to contact each other, a predetermined welding current is applied, thereby joining the portions of the circuit pattern layers on the front side and the back side which face each other.
In the antenna circuit constituent body, as a method of electrically connecting both end portions of the antenna circuit pattern layer formed on the one of the surfaces of the base material without forming the bridge circuit pattern layer on the other of the surfaces of the base material, the below-described methods are available.
(4) As disclosed in Japanese Patent Application Laid-Open Publication No. 2001-92936 (Patent Literature 4) and Japanese Patent Application Laid-Open Publication No. 2005-109505 (Patent Literature 5), an antenna circuit pattern layer is formed on one of surfaces of a base material, an insulating layer is formed by applying an insulating resin onto one portion of the antenna circuit pattern layer, which intersects a jumper circuit pattern layer, and a conducting substance such as a silver paste is applied onto the insulating layer so as to electrically connect portions to be joined at both end portions of the antenna circuit pattern layer, thereby forming the jumper circuit pattern layer.
(5) As disclosed in Japanese Patent Application Laid-Open Publication No. 2010-28706 (Patent Literature 6), respective tips of one end portion and the other end portion of a conductive linear body are stuck through both respective end portions of an antenna circuit pattern layer, which are to be electrically connected, from the other surface of a base material so as to penetrate through the base material and the antenna circuit pattern layer formed on one surface of the base material, thereby extending a central portion of the linear body on the other surface of the base material, disposing the one end portion of the linear body on a surface of one end portion of the antenna circuit pattern layer, and disposing the other end portion of the linear body on a surface of the other end portion of the antenna circuit pattern layer.